000
FXUS65 KPSR 080916
AFDPSR
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PHOENIX AZ
215 AM MST MON SEP 8 2008
SOUTH-CENTRAL AND SOUTHWEST ARIZONA...AND SOUTHEAST CALIFORNIA
FORECAST DISCUSSION
.SYNOPSIS...
SHOWERS AND THUNDERSTORMS WILL REMAIN POSSIBLE ACROSS THE DESERT
SOUTHWEST FOR THE NEXT SEVERAL DAYS AS A BROAD LOW PRESSURE SYSTEM
LOOMS OVER THE REGION. THE MOUNTAINS OF CENTRAL AND EASTERN ARIZONA
WILL BE THE MOST LIKELY AREAS TO SEE RAINFALL THROUGH WEDNESDAY.
RAIN CHANCES WILL BEING TO TAPER OFF THURSDAY AS THE LOW PRESSURE
SYSTEM MOVES TO THE EAST. TEMPERATURES WILL BE ON A COOLING TREND
THROUGH THURSDAY WITH A MINOR UPWARD TREND TOWARD THE WEEKEND.
&&
.DISCUSSION...
NOT MUCH CHANGE IN THE FORECAST LOGIC FOR THE NEXT FEW DAYS AS THE
MAJORITY OF MODELS ARE ON THE SAME PAGE THROUGH WEDNESDAY BUT
DIFFER BEYOND. SHEAR ZONE CURRENTLY PARALLELING OUR CWA IS
PROVIDING TO BE THE BREEDING GROUNDS FOR SEVERAL WEAK SHORTWAVES
WHICH WILL BE KICKED ACROSS OUR CWA BY AN APPROACHING...MORE
SIGNIFICANT...SHORTWAVE DOWN THE SIERRAS. DUE TO OUR RATHER DRY
BOUNDARY LAYER STILL EXPECTING TODAY TO BE MORE OF A /RAMP UP/ DAY
HENCE THE TEMPERED POPS. SHOULD BE ENOUGH ENERGY AND INSTABILITY IN
THE ATMOSPHERE TO GET MOUNTAIN-TOP TSTMS GOING. THE INCREASING
CLOUDS AND MOISTURE WILL HELP BRING TEMPERATURES DOWN SEVERAL
DEGREES TODAY AS COMPARED TO YESTERDAY.
SREF POPS CONTINUE TO PEG TUESDAY AS A BIG DAY FOR THE MOUNTAINS OF
ERN AZ. HAVE CONTINUED THE TREND FROM PREVIOUS SHIFTS AND INCREASED
POPS TUESDAY. STILL NOT TERRIBLY EXCITED ABOUT CONVECTION ACROSS THE
PHX AREA AS STORM MOTION WILL BE SW AT 10-20KT...NOT IDEAL FOR OUR
OFT REQUIRED BOUNDARY LAYER AIRMASS COLLISIONS. I DID HIT THE POPS
HARDER FOR SRN GILA COUNTY INCLUDING THE GLOBE AREA. OUTSIDE CHANCE
OF SEEING SVR STORMS IN THAT AREA TUESDAY WITH A PRIMARY THREAT OF
HAIL.
WEDNESDAY SHOULD SEE THE BEGINNING OF A DOWNWARD TREND IN POPS AS
THE PRIMARY MOISTURE PLUMES BEGINS TO MOVE EAST INTO NM AND TX. A
LOT WILL DEPEND ON HOW A SHORTWAVE PROGGED TO MOVE INTO THE GREAT
BASIN BEHAVES. IT IS AT THIS POINT THAT THE MODELS BEGIN TO
DIVERGE...WITH THE GFS BECOMING MORE REGRESSIVE WITH THE FLOW
PATTERN THROUGH THE WEEKEND WHILE THE ECMWF REMAINS MORE PROGRESSIVE
WITH THE SHORTWAVE. IF THE GFS VERIFIES WE/LL HAVE A LOT MORE CLOUDS
AND PRECIP HANGING AROUND POSSIBLY INTO THE WEEKEND AS THE LOW HANGS
TO OUR SW AND ADVECTS MOISTURE INTO THE AREA...POSSIBLY FROM
TROPICAL STORM LOWELL /CURRENTLY WELL SOUTH OF THE BAJA TIP/. IF THE
ECMWF VERIFIES WOULD MEAN FAIRLY DRY WEATHER BY THURSDAY OR FRIDAY.
THE GFS ENS MEAN SUPPORTS THE OPERATIONAL GFS...WHICH ISN/T TOO
SURPRISING.
BUT THE LACK OF CONSISTENCY WRT THE FLOW PATTERN FOR LATE THIS WEEK
INTO THE WEEKEND RESULTS IN A LOW CONFIDENCE FORECAST. WILL PLAY IT
CONSERVATIVELY FOR NOW AND JUST MAKE MINOR CHANGES TO THE GOING
FORECAST...WITH A DECREASING TREND IN POPS AND CLOUDS FROM THURSDAY
ON OUT. TEMPS CURRENTLY FORECAST TO BOTTOM-OUT ON THURSDAY WITH
MINOR FLUCTUATIONS THEREAFTER.
&&
.AVIATION...
SOUTHEAST CA AND SOUTHWEST AZ...INCLUDING KBLH...KNYL...AND KIPL
AIRFIELDS. ISOLATED SHOWERS AND THUNDERSTORMS WILL CONTINUE NEAR
THE ABOVE AIRFIELDS THROUGH 06Z MON. GUSTY AND VARIABLE WINDS 15 TO
25 KNOTS ARE POSSIBLE...ALONG WITH SCT TO BKN CLOUDS AOA 15 THSD
MSL. AFTER 06Z MON...EXPECT SCT CLOUDS BASED NEAR 15 THSD MSL AND
LIGHT WINDS THROUGH 18Z. AFTER 18Z MON...AND THROUGH 04Z TUE...
ISOLATED AFTERNOON AND EARLY EVENING SHOWERS AND THUNDERSTORMS...
ALONG WITH GUSTY AND VARIABLE SURFACE WINDS BETWEEN 15 AND 25 KNOTS
ARE FORECAST.
SOUTH CENTRAL AZ...INCLUDING KPHX AND KIWA AIRFIELDS. SCT TO BKN
CLOUDS AOA 14 THSD MSL ...WITH ISOLATED SPRINKLES OR LIGHT SHOWERS
POSSIBLE THROUGH 08Z MON. AFTER 08Z...SCT TO BKN CLOUDS AOA 14 THSD
MSL WITH LIGHT EAST WIND UNDER 10 KNOTS. BETWEEN 20Z MON AND 04Z
TUE...SCT CLOUDS BASED NEAR 10 THSD MSL WITH LIGHT WIND. ALSO...
ISOLATED MOUNTAIN THUNDERSTORMS WITH TOPS TO 35 THSD ARE POSSIBLE 60
TO 80 MILES NORTH THROUGH SOUTHEAST OF KPHX.
AVIATION DISCUSSION NOT UPDATED FOR AMENDED TAFS.
&&
.FIRE WEATHER...
TUESDAY THROUGH FRIDAY...AN AREA OF LOW PRESSURE WILL DEVELOP OFF
THE COAST OF SOUTHERN CALIFORNIA...BRINGING A SLIGHT CHANCE OF
SHOWERS AND THUNDERSTORMS TUESDAY FOR THE ENTIRE FORECAST
AREA...WITH A BETTER CHANCE IN THE HIGHER TERRAIN OF CENTRAL
ARIZONA. SLIGHT CHANCES OF THUNDERSTORMS WILL CONTINUE WEDNESDAY AND
THURSDAY IN THE HIGHER TERRAIN AREAS OF SOUTHERN GILA COUNTY.
TEMPERATURES WILL REMAIN NEAR SEASONAL NORMALS...WHILE AFTERNOON
HUMIDITY VALUES WILL RANGE FROM THE MID-TEENS IN SOUTHEAST
CALIFORNIA TO THE MID-TWENTIES IN SOUTH-CENTRAL ARIZONA.
&&
.PSR WATCHES/WARNINGS/ADVISORIES...
AZ...NONE.
CA...NONE.
&&
$$
NATIONAL WEATHER SERVICE PHOENIX IS ON THE INTERNET AT
WEATHER.GOV/PHOENIX
DISCUSSION...INIGUEZ
AVIATION...VASQUEZ
FIRE WEATHER...ROGERS
